.calendar{
    border: 1px solid #aaa;
    padding: 10px;
    width: 300px;
    height: 250px;
}
.header{
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 40px;
}
.content{
    display: grid;
    grid-template-columns: repeat(7,1fr);
    text-align: center;
    line-height: 30px;
}
.day:hover,.selected{
  background-color: #ccc;
  cursor: pointer;
}